# CVE-2026-80673: ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find()

> A crafted NTFS image triggers an out-of-bounds read in the Linux kernel, potentially leaking memory or causing a crash.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-80673, GHSA-hmfm-f852-mmj6, UBUNTU-CVE-2026-80673

## What is CVE-2026-80673?

CVE-2026-80673 is a critical memory corruption vulnerability in Linux, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find()

When resolving an attribute lookup with a non-zero @lowest_vcn,
ntfs_external_attr_find() peeks at the next $ATTRIBUTE_LIST entry to
decide whether to keep searching, but bounds that not-yet-validated
entry only with "(u8 *)next_al_entry + 6 < al_end" (which proves just
bytes 0..6 are in range) and "(u8 *)next_al_entry + length <= al_end"
with an attacker-controlled, non-8-aligned length. It then reads
next_al_entry->lowest_vcn (an __le64 at offset 8) and the name at
next_al_entry->name_offset, both of which can lie past al_end -- the
exact end of the kvmalloc'd attribute-list buffer (allocated at the
on-disk attr_list_size, no rounding). A crafted on-disk $ATTRIBUTE_LIST
whose last entry sits a few bytes before al_end therefore yields a slab
out-of-bounds read when the inode is read.

Validate the look-ahead entry with ntfs_attr_list_entry_is_valid() (added
in patch 1/3) before dereferencing lowest_vcn and the name, so the same
fixed-header, length and name bounds the main attribute-list walk uses now
guard this read too.

## Which versions are affected by CVE-2026-80673?


## How do I fix CVE-2026-80673?

Apply the vendor's patch.

## Is CVE-2026-80673 being exploited?

There is no known exploitation of CVE-2026-80673 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80673 and fix it if it is affected.

What it is: CVE-2026-80673 is a critical memory corruption vulnerability in Linux, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80673 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-80673/ (Markdown: https://insights.sbomify.com/CVE-2026-80673/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80673
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80673
- OSV: https://osv.dev/vulnerability/CVE-2026-80673

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80673/
Summaries are generated and may contain mistakes; the official description above is the record.